Interacting Electrons on a Square Fermi Surface

Electronic states near a square Fermi surface are mapped onto quantum chains. Using boson-fermion duality on the chains, the bosonic part of the interaction is isolated and diagonalized. These interactions destroy Fermi liquid behavior. Non-boson interactions are also generated by this mapping, and give rise to a new perturbation theory about the boson problem. A case with strong repulsions between parallel faces is studied and solved. There is spin-charge separation and the square Fermi surface remains square under doping. At half-filling, there is a charge gap and insulating behavior together with gapless spin excitations. This mapping appears to be a general tool for understanding the properties of interacting electrons on a square Fermi surface.Comment: 25 pages, Nordita preprint 94/22

Energy dependent Schrödinger operators and complex Hamiltonian systems on Riemann surfaces

We use so-called energy-dependent Schrödinger operators to establish a link between special classes of solutions on N-component systems of evolution equations and finite dimensional Hamiltonian systems on the moduli spaces of Riemann surfaces. We also investigate the phase-space geometry of these Hamiltonian systems and introduce deformations of the level sets associated to conserved quantities, which results in a new class of solutions with monodromy for N-component systems of PDEs. After constructing a variety of mechanical systems related to the spatial flows of nonlinear evolution equations, we investigate their semiclassical limits. In particular, we obtain semicalssical asymptotics for the Bloch eigenfunctions of the energy dependent Schrödinger operators, which is of importance in investigating zero-dispersion limits of N-component systems of PDEs

Observations of long period waves in the tropical oceans and atmosphere

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Woods Hole Oceanographic Institution February 1980The existence of resonant, baroclinic, equatorially-trapped inertia-gravity waves (discovered by Wunsch and Gill (1976)) is confirmed in the mid-Pacific by spectral analysis of long sea level records. The energy of the low-mode inertia-gravity waves is found to decrease toward the meridional boundaries. A simple spectral model, acknowledging the dispersive characteristics of the equatorial waves, adequately reproduces the observed mid-Pacific sea level spectra in the 1-6 day band. Model spectra computed at latitudes outside the equatorial waveguide of the gravest meridional modes suggest the presence of "inertial" peaks in several observed sea level spectra. Resonant, low-mode inertia-gravity waves may also exist in the Indian Ocean. Sea level fluctuations along the Pacific equator are found to have Kelvin wave characteristics in the 35-80 day band, and, in particular, propagation from the western Pacific to the coast of South America is observed. The Kelvin waves are atmospherically-forced in the central- western Pacific and have a computed equivalent depth corresponding to the first-baroc1inic mode. Outside of the equatorial mid-Pacific, a non-static ocean response to air pressure in the 4-6 day band is dominated by a basin-wide, barotropic, planetary mode. The low Q of this mode suggests that the ocean is viscous with respect to large-scale barotropic oscillations. The dynamical components of the observed long-period tides have been isolated for the first time using the "self-consistent" equilibrium tide of Agnew and Farrell (1978). The tides are slightly non-equilibrium with large horizontal scales. The relatively short-scale Rossby modes predicted by Wunsch (1967) are not observed, perhaps because of the poor spatial coverage of the dataset. Considering the low Q of the 4-6 day planetary basin mode, it is suggested that the long-period tides are frictionally-controlled. The 4- and 5-day equatorial inertia-gravity waves, the 35-80 day Kelvin waves and the 4-6 day planetary basin mode are clearly atmospherically forced, and, perhaps surprisingly, they are forced by atmospheric waves that have similar horizontal structures, i.e., 4-5 day Rossby-gravity waves, 40-50 day Kelvin waves and a 5-day global barotropic mode. The surface expressions of these atmospheric waves are determined in order to understand the nature of the oceanic response, e.g., resonant or forced. Much of the information about the surface atmospheric fields that has been collected, including frequency-wavenumber descriptions, awaits an accurate model of the coupling between wind stress and internal ocean waves.Monetary support for this research was provided by the National Science Foundation through contract OCE73-0l384. At various times, tuition and living expenses were paid by funds from the NSF contract above, the Office of Naval Research (contract N00014-C-75-029l), the Cecil and Ida Green Professorship in Earth Sciences, the J. P. Luther Educational Fund and by an M.I.T. Educational Tuition Award

Letter to Sonora Dodd from Luther S. Beard, May 23, 1911

Letter to Sonora Dodd, from Luther S. Beard, News Editor for The North American.https://digitalcommons.whitworth.edu/fathers-day-correspondence/1011/thumbnail.jp

Snow cover monitoring by machine processing of multitemporal LANDSAT MSS data

LANDSAT frames were geometrically corrected and data sets from six different dates were overlaid to produce a 24 channel (six dates and four wavelength bands) data tape. Changes in the extent of the snowpack could be accurately and easily determined using a change detection technique on data which had previously been classified by the LARSYS software system. A second phase of the analysis involved determination of the relationship between spatial resolution or data sampling frequency and accuracy of measuring the area of the snowpack

A Follow-up Study of the 1962-66 Graduates Augustana Academy

The functions of the guidance program in today\u27s schools usually consist of five main services. They are: inventory, information, counseling, placement, and follow-up. This paper will center about the last of these services, namely, follow-up. The follow-up service is to education what the customer relations department is to merchandising by means of a continuing follow-up of former students, the educator learns of their .failures, problems, successes, and--most important--obtains their suggestions for improvement. The purpose of this investigation was to conduct a follow-up study of the 1962-66 graduates of Augustana Academy, Canton, South Dakota. Information concerning their evaluations of their former school, their opinions of it, and their_ present status were sought in this survey. At the present time, Augustana Academy is undergoing a retooling operation. With this in mind, it is necessary to evaluate the present curriculum and guidance services. The main purpose of this study was to aid in these revisions

WHEAT BUFFER STOCKS AND TRADE IN AN EFFICIENT GLOBAL ECONOMY

This study assesses storage and trade of wheat in an integrated global economy. Domestic and international linkages are analyzed using a dynamic rational expectations model of the world wheat market. The results of this study demonstrate the importance of endogenizing both storage and trade in studying commodity markets. Results suggest an optimal US buffer stock level of 150 million bushel. Results indicate that past government stockholdings have not followed efficient market outcomes. Private markets likely would perform better in the absence of government market distortions. Results indicate that elimination of the Export Enhancement Program by the US and of export restitution payments by the EU is unlikely to have a major impact on wheat exports from the two regions, but will save millions of tax dollars in both regions.Crop Production/Industries, International Relations/Trade,

STRUCTURE OF FARMING UNDER FREER TRADE AMONG NAFTA COUNTRIES

International Relations/Trade,

Geometric analysis of optical frequency conversion and its control in quadratic nonlinear media

We analyze frequency conversion and its control among three light waves using a geometric approach that enables the dynamics of the waves to be visualized on a closed surface in three dimensions. It extends the analysis based on the undepleted-pump linearization and provides a simple way to understand the fully nonlinear dynamics. The Poincaré sphere has been used in the same way to visualize polarization dynamics. A geometric understanding of control strategies that enhance energy transfer among interacting waves is introduced, and the quasi-phase-matching strategy that uses microstructured quadratic materials is illustrated in this setting for both type I and II second-harmonic generation and for parametric three-wave interactions